old_string = 'hello woRld'
upper_str = old_string.upper()
lower_str = old_string.lower()
cap_str = old_string.capitalize()
title_str = old_string.title()
print(f'upper方法:{upper_str}')
print(f'lower方法:{lower_str}')
print(f'capitalize方法:{cap_str}')
print(f'title方法:{title_str}')